Air Transport in Vortex‐flow Drop Shafts

Abstract

The effect of swirl on air transport in a vertical drop shaft is described. Laboratory experiments on a vortex‐flow drop shaft showed that most of the air is entrained in the annular hydraulic jump that is formed when the annular jet flow changed to the pipe‐full flow. A significant portion of the air bubbles converged due to an inward pressure gradient toward the center of the drop shaft, coalesced to form large bubbles, and then rose toward the surface. A large number of air bubbles still were carried downstream for flow conditions where the jump occurred at the location of low circulation. The air transport rate down the drop shaft was virtually zero if the jump formed in the strong circulation flow‐region. The theoretical analysis indicates that the amount of air transported downstream depends upon the swirl number. The air concentration decreases with the increase in the swirl number.